Refractory material and process for producing it.



NITE STATES PATET FI IQE.

CHARLES L. NORTON, or MANcnESrEii, MASSACHUSETTS, ASSIGNOR TU ASBESTOS WOOD COMPANY, A CORPORATION or MAINE.

REFRAGTQRY ATEREAL AND PRIOOESS FOR FQDUCHNG H.

Specification of Letters Patent.

Patented March 12, 1907.

Application filed June 7,1906. Serial No. 320,670.

To all whom it may concern Be it known that I, CHAR ES L. NORTON, a

' 'citizen ofahe United States, and a resident of Manchester, in the county of Essex and State of Massachusetts, have invented new-and useful Improvements in Refractory Materials and Processes for Producing Them, of

. which the following is a specification.

My invention relates to the art of produc:

ing refractory materials from substances of composition of matter irrespective of form,

proportions, or specific utility.

The material which I. employ as the main basis for my new processand product is asbestiform fiberthat is to say, inorganic fibrous material which is composed chiefly of and sometimes wholly of silicate of magnesia-which appears in nature as asbestos? (popularly so called) or the serpentine rpck which forms the natural matrix forasbestos or as modifications of hornblende. With this basic material I employ a bonding material which with the asbestiform'basic material en- .ters into a mutual relation which I believe involves a more intimate association than mere mechanical 00l16S1OI1. The bonding material which I select for this purpose is magne-' .sium oxid, (whichmay be obtained by calcination of magnesium carbonate,)-which when associated with asbestiform fiber andwater under proper conditions of pressure knits or bonds the compound mass into a uniform,

homogeneous, and practically indestructible substance.

I have-observed that the serpentine,wh ich is closely associated in nature with fibrous asbestos, though apparently a rock which reduces mechanically to a hard granular gravel, will when still furthercomminuted by grinding become reduced to a pulp which instead of being a fine dust or assemblage of hard minute granules is itself also essentially fibrous and closely analogous in its character and feel to a mass of pulped asbestos fibers.

' purpose.

The pulped serpentine discloses under the microscope a fibrous structure, the individual particles being extremely short and fine. Serpentine pulp being an asbestiform fiber, is well adapted to use as the basic material for my process and product. It may be mixed with longer asbestos fiber, if desired, but for most purposes may be used without such admixture. I This circumstance I regardas of considerable practical importance, ecause, so far as I am informed, the ser entine matrix, of asbestos has heretofore hben regarded as mere waste material without any commercial value. As the proportionate quantity of serpentine which has to be worked to obtain commercial asbestos is very large, the advantage of using the waste rock instead of the more valuable longer-fibered asbestos is obvious;

In preparing magnesium oxid for my bonding material I first reduce. a substantially pure magnesite or magnesium carbonate to a e powder, say, fine enough to pass through a screen of one hundred and forty mesh. Comminution of magnesium carbonate facilitates its thorough and uniform calcination. Moreover, the magnesium oxid produced by calcination of a finely-powdered carbonate is correspondingly comminuted, and I have discovered that the bonding orcementitious property of the oxid increases to a remarkable degree as the particles thereof are decreased in size. The calcination should not be excessive. A dull red heat will effect the proper calcination satisfactorily. If the magnesite (magnesium carbonate) is put in the kiln in lumps, as limestone is, the calcination is liable to be confined to the surface of the lumps unless the heat employed be intense,

when, though the whole of each lump may be calcined,-the exterior is liable to be over-calcined and proportionately unsuitable to my Magnesium oxid may be obtained from other sources and by other processes, and if used in the manner hereinbelow described will serve the purpose.

As the comminution of the magnesium oxid employed is an important factor in the process, I have used in practice a precipitated .magnesrumcarbonate, such as is obtained by the chemical reduction of dolomite, whereby the ma nesium carbonate is separated from thecaI gether in that substance. This preci itated magnesium carbonate is an impalpab e powcium carbonate which exists to-- der capable of sifting freely through boltingcloth, and from the calcination thereof I obtain a magnesium oxid which is correspondingly comminuted and whose cementing capacity under the conditions of my process hereinbelow described is very high.

Having procured asbestiform fiber (preferably pulped serpentine, either with or without longer fibers of similar character) and properly comminuted magnesium oxid, I mix the two intimately, using any suitable mixing-machine for the purpose, employing proportions of about eighty per cent. asbestiform fiber and twenty per cent. magnesium oxid, by weight. The magnesium oxid should be used when it is fresh-i. a, before hydration has set in to any considerable degreebecause I have observed that the proccess of forming my new composition of mat ter should be carried. on while hydration of the ma nesium oxid is in progress or at least before hydration is completed. If, therefore, the oxid has been hydrated to any considerable degree before my process is per formed the resuft will be correspondingly imperfect. The proportions of fiber and magnesium oxid may be varied without substantial departure from my process and without varying the product thereof except in degree. As a rule, if the proportion of bonding material (magnesium oxid) is'increased the consistency of the product becomes more stony, whereas if the basic asbestiform fiber is increased in proportion to the bonding material the product becomes more woody, though in neither case is any lamination or grain observable in the product.

When the compound of asbestiform fiber base and magnesium oxid is well mixed, I make a pulp thereof with water. No strict rule as to the proportion of water need be observed, because the succeedin step in the process takes care of any reasonable excess of water that may be present. Upon the addition of water to the mixture hydration begins, and while hydration is in progress I place the wet pulp on a filter-press in any suitable box or mold and apply pressure to the pulp. The surplus water is squeezed out, coming from the press substantially clear, although it may contain one or both of the main ingredients in solution or suspension to a trifling degree. I employ a pressure of from fifteen hundred to two thousand five hundred pounds per square inch of superficial area of the pulp in the mold. As the surplus water is expressed from the mass and the effective pressure thereon increases the behavior of the mass of pulp appears to be determined when a critical pressure is reached. This critical pressure cannot be exactly determined beforehand. In practice I have found it to be within the limits stated above. When it is reached, the mass, though composed of solid particles originally and though the surplus of water has been for the most part, at least, expressed, behaves more like a homogeneous liquid than a solid 1 in that great lateral pressure is exerted on the mold or box. 1 believe that when pressure is brought to bear on the mixture during the progress of hydration the particles of as- .bestiform fiber and calcined magnesium carbonate become, as it were, mutually soluble. They come apparently to a state of flux when the critical pressure is attained, and this arrival at a state of flux marks the attainment of the critical pressure. Whether this be the true explanation or not, the mass under pressure takes a preliminary set and may be removed from the mold as a solid slab, block, or molded article. The preliminary set is, however, not the final stage in the manufacture. Time should be given for a permanent set to take place; otherwise the molded object is liable to sag, warp, or bend from its true form. Therefore I place the molded article upon a proper support, or preferably four hours to several days, according to the shape or bulk of the object itself. During this period thepermanent set takes place, and afterward the moldedarticle is ready for use.

The proportions, size, and weight of the piece of compressed composition which comes from the mold will determine the charaeter of support or pressure desirable during the secondary setting. Some objects of small size or simple shape need only be laid on a support. Others will require firmer holding during this period. The secondary or final setting of the productis due, I believe, to dehydration of the hydrated oxid. This dehydration probably involves only a partial loss of the water originally taken up. Heatsay that obtainable from a steamheated support or press-will accelerate the "trical insulator, can be worked with tools,

bored, nailed, screwed, is sufficiently stiff and strong to be used for door-frames or doors, takes a high polish, and receives and holds superficial coats of paints or varnishes readily. 4

- mixture of magnesium oxid and water, ex-

h until it sets permanently. v

8. The process of treating asbestiform fiber droxid in intimate mixture with the fiber,

conditions conducive to the formation of mixture of magnesium oxidand water, and

'cient to produce therein a condition of flux.

I claim as my invention 1. The process of treating asbestiform fiber which consists in forming magnesium byunder pressure. 1

2. The process of treatingasbestiform fiber which consists in making with the fiber a. mixture .ofmagnesium oxid and water, and compacting'the solids under pressure while wet.

I 3. The process of treating asbestiform fiber which consists in makingwith the fibera pressing the excess of water and compacting the solids under pressure while wet.

4. The process of treating asbestiform fiber which consists in makin with the fiber a mixture of magnesium" oxid and water under magnesium hydroxid, and compacting the solid ingredients under pressure while wet.

5. The process of treating asbestiform fiber which consists in making with the fiber a mixture of magnesium oxid and water, and compacting the solids under pressure While hydration is in process.

6. The process oftreating' a'sbestiform fiber which consists in making with the'fiber' a compacting the solids under pressure suffi- -7. The process-of treating asbestiform fiber which consists in making with the fiber a mixture of ma esium oxid and water-,compactingthe so ids under pressure while wet, until they assume a preliminary set, and thereafter supporting the resulting product which consists in making with the fiber a mixture of ma esium 03nd and water, compactingthe so ids under pressure while wet until they assume a preliminary set, and thereafter subjecting the resulting product to reduced pressure until it sets permanently.

9. The process of treating asbestiform fiber which consists in'making with the fiberva mixture of calcined precipitated magnesium carbonate, and water, and compacting the solids by pressure while wet.

10. The process of treating asbestiform fiber which consists in making with the fiber .a mixture of calcined precipitated magnesium carbonate and water, and compacting the solids under pressure while hydration is in process.

11. The processofv treating asbestiform fiber. which consists in mixing a substantial preponderance (by weight) of fiber, with magnesium oxid and water, and subjecting this 4th day of June, 1906.

, CHARLES L. NORTON.

.Witnesses: v p

ODIN B. Ronnn'rs, 

